High mobility group protein (HMG-1) is a non-histone DNA binding protein that facilitates transcription. Recently, investigators have shown that HMG-1 has other roles that may be critical in the development of sepsis and septic shock. HMG-1 is released as a late mediator of sepsis (i.e., after 8 to 15 hours) from mononuclear cells stimulated with TNF, IL-1, or endotoxin. It is detected in the blood of septic mice and in septic patients and it worsens outcome when given to septic mice. It plays a role in migrating axons of neurons in the developing brain and it activates plasminogen. Some of the actions are through the RAGE receptor (receptor for advanced glycation products) which plays a role in chronic inflammation in diabetes. This novel axis of inflammation remains to be characterized in human sepsis. In order to study the target cells and contribution of HMG-1 to acute human inflammation, we are producing recombinant human HMG-1 in a bacterial expression system and are using the protein to study inflammatory responses in endothelium and mononuclear cells including alveolar macrophages. In addition, we are developing biologically active peptide fragments of the intact molecule in order to study structure function relationships. Cell lines and migrating human cells from humans challenged with endotoxin will be studied for the expression of RAGE and their responses to HMG-1. HMG-1 will also be studied in blood and inflammatory lavage obtained from volunteers challenged with endotoxin (protocol 92-CC-0141). Oligonucleotide gene arrays will be used to study the inflammatory axis initiated by HMG-1 on target cells. These data should provide important new information regarding the role of HMG-1 in acute human inflammation to bacterial products.